US5959302A - High resolution radiographic imaging device - Google Patents

High resolution radiographic imaging device Download PDF

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US5959302A
US5959302A US08/863,527 US86352797A US5959302A US 5959302 A US5959302 A US 5959302A US 86352797 A US86352797 A US 86352797A US 5959302 A US5959302 A US 5959302A
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electrode
illumination beam
space
amplification
elementary
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Georges Charpak
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EOS Imaging SA
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J47/00—Tubes for determining the presence, intensity, density or energy of radiation or particles
    • H01J47/02—Ionisation chambers
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B6/00—Apparatus or devices for radiation diagnosis; Apparatus or devices for radiation diagnosis combined with radiation therapy equipment
    • A61B6/42—Arrangements for detecting radiation specially adapted for radiation diagnosis
    • A61B6/4208—Arrangements for detecting radiation specially adapted for radiation diagnosis characterised by using a particular type of detector
    • A61B6/4258—Arrangements for detecting radiation specially adapted for radiation diagnosis characterised by using a particular type of detector for detecting non x-ray radiation, e.g. gamma radiation

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  • the invention relates to a high resolution radiographic imaging device.
  • the present radiographic imaging devices are subject to two essential constraints: increasing the resolution of the images obtained and reduction of the radiation doses applied to the subject to be observed, in particular by reduction of the time of exposure of the latter to the ionizing radiation.
  • the use of very high resolution detector elements, and therefore of very small size and having a high amplification gain is susceptible to allow an appropriate distribution of a plurality of this type of detector element over a specific observation field and consequently a reduction in the illumination time necessary for the observation of this field to that necessary for the observation of an elementary field corresponding to that of one detector element, which consequently makes it possible to reduce significantly the radiation doses applied to the subject to be observed.
  • a purpose of the present invention is the use of a high resolution radiographic imaging device making it possible to satisfy the constraints mentioned above.
  • Another purpose of the present invention is the use of a radiographic imaging device in which the image resolution is better than 100 ⁇ m.
  • Another purpose of the present invention is the use of a radiographic imaging device in which the time of exposure of a subject can be reduced by a factor of 10 with respect to the devices of the prior art.
  • the detector module comprises at least one ionizing particles detector comprising at least one gas chamber provided with an inlet window for the illumination beam.
  • the gas chamber comprises a first, a second and a third flat electrode, each flat electrode being placed parallel with one another in order to form a space for the conversion of the illumination beam into electrons and a space for the amplification of these electrons.
  • the inlet window is placed at the level of the conversion space in order to ensure the inlet of the illumination beam into the conversion space and the amplification space has a multiplication length, the distance separating the second and the third electrodes, of less than 200 ⁇ m.
  • the detector furthermore comprises a biasing circuit making it possible to raise the first electrode to a first electrical potential, the second electrode to a second electrical potential higher than the first electrical potential, and the third electrode to a third electrical potential higher than the second electrical potential.
  • the second electrode pierced with holes forms a cathode allowing the transmission of the electrons generated in the conversion space towards the amplification space, and the third electrode forms an anode constituted by a plurality of electrically isolated elementary anodes.
  • the electrical potentials applied to the first, to the second and to the third electrodes allow the generation of a first and a substantially parallel second electrical field in the conversion space and in the amplification space, each of these fields being substantially perpendicular to the electrodes with an amplitude ratio greater than 10 in order to ensure the multiplication of these electrons in the amplification space by an avalanche phenomenon, confined to the amplification length, and to generate multiplied electrons in the vicinity of the third electrode forming an anode.
  • Circuits for detecting and counting the multiplied electrons are coupled to the elementary anodes forming the anode.
  • the high resolution radiographic imaging device is applicable both to industrial radiographic imaging, in particular in the fields of crystallography and strength of materials, and to medical radiographic imaging.
  • FIGS. 1a and 1b show a longitudinal cross-sectional view of a high resolution radiographic imaging device which is the subject of the present invention
  • FIGS. 1c and 1d show a cross-sectional view along the transverse cross-section plane AA of FIG. 1a relative to a first and to a second variant embodiment of the high resolution radiographic imaging device which is the subject of the present invention
  • FIG. 2a shows a detail of the embodiment of specific detection circuits used by the high resolution radiographic imaging device according to the invention
  • FIG. 2b shows a detail of an advantageous embodiment of the grid forming the cathode of a detection element according to the subject of the present invention
  • FIGS. 3a and 3b show an advantageous embodiment of a high resolution radiographic imaging device according to the invention, wherein a multi-channel structure is placed in the ionizing radiation conversion space of a detector element used by this device, and a detail of the embodiment of this multi-channel structure;
  • FIGS. 4a to 4d show a variant embodiment of the high resolution radiographic imaging device, which is the subject of the invention, wherein a capacitive coupling circuit is used to ensure the detection of the electrons generated by the ionizing radiation;
  • FIGS. 5a and 5b show another variant embodiment of the high resolution radiographic imaging device, which is the subject of the invention, wherein the detection of the electrons generated by the ionizing radiation is carried out by means of the creation of luminous avalanche phenomena;
  • FIG. 5c shows a high resolution radiographic imaging device according to the subject of the present invention using ⁇ imaging
  • FIGS. 6a and 6b show a high resolution radiographic imaging device according to the subject of the present invention, wherein a plurality of elementary detector elements are arranged by superimposition, in such a way as to allow a three-dimensional analysis of a given subject for an illumination beam having a predetermined solid angle.
  • FIGS. 1a and 1b A more detailed description of a high resolution radiographic imaging device using ionizing radiation, according to the subject of the present invention, will now be given with reference to FIGS. 1a and 1b.
  • FIG. 1a is a cross-sectional view along a plane of longitudinal symmetry of this device, this plane of longitudinal symmetry being, by definition, the plane of the paper on which FIG. 1a is shown.
  • the device according to the invention comprises an ionizing radiation source, referenced S, delivering ionizing radiation in the form of a divergent beam, and a longitudinal slot, referenced F, forming a diaphragm, allowing the delivery of an illumination beam.
  • this illumination beam is a flat beam of X or ⁇ (gamma) rays substantially distributed in the plane containing the longitudinal slot F, that is to say in a plane perpendicular to the plane of the paper on which FIG. 1a is shown.
  • the said illumination beam makes it possible to illuminate a subject SU to be observed, this illumination beam, after selective absorption according to the density zones of the subject to be observed SU, being received by a detection module, referenced 1 in the said FIG. 1a.
  • the detection module 1 comprises at least one ionizing particles detector comprising a gas chamber 10, provided with a window for the inlet of the illumination beam.
  • the gas chamber 10 is a chamber of the conventional type having a window for the inlet of the flat illumination beam, the window being referenced Fe, and elements for the inlet of a filling gas, these inlet elements not being shown in the drawings in order not to complicate the latter.
  • the gas let into the gas chamber can, in a conventional way, be inlet under a slight excess pressure with respect to atmospheric pressure or, on the contrary, either at a relatively high pressure, or at a very low pressure, close to a few Torr, depending on the operating conditions of the radiographic imaging device which is the subject of the invention.
  • the gas chamber 10 comprises a first electrode, referenced 11, a second electrode, referenced 13, and a third electrode, referenced 14, these electrodes being flat and placed parallel with one another in order to form a conversion space, referenced 12, for converting the illumination beam into electrons, and a space for amplification by multiplication of these electrons, this amplification space being referenced 15.
  • the inlet window Fe is placed at the level of the conversion space 12 and makes it possible to ensure the inlet of the illumination beam into the conversion space 12 parallel with the first electrode, 11, and with the second electrode, 13, in the case of the embodiment shown in FIG. 1a.
  • the inlet window Fe is thus placed laterally on the gas chamber 10 in order to allow the inlet of the illumination beam parallel with the cathode 13 and anode 14 electrodes.
  • the inlet window Fe is placed on the face of the gas chamber located opposite the second cathode electrode 13 in order to allow a frontal inlet of the illumination beam with respect to the electrodes.
  • the assembly constituted by the source S, the slot F materialized by a diaphragm made of lead for example, and the detector module 1 can be rendered integral by means of a frame B, this assembly being able to be manoeuvred in translation and, if necessary, in rotation, in order to ensure an appropriate analysis of the subject SU.
  • the mechanical embodiment of the assembly will not be described in detail because the elements necessary for this embodiment are known to those skilled in the art.
  • the source S and the detector module 1 can be fixed, the subject SU being moved with an appropriate displacement.
  • the amplification space 15 has a multiplication length, that is to say a distance D separating the second electrode, 13, and the third electrode, 14, of less than 200 ⁇ m.
  • the latter comprises a biasing circuit, referenced 2, making it possible to raise the first electrode 11 to a first electrical potential, the second electrode 13 to a second electrical potential higher than the first one, and the third electrode 14 to a third electrical potential higher than the second electrical potential.
  • the biasing circuit mentioned above can comprise a dc power source, referenced V 13 , whose positive electrode is connected to the reference voltage V REF and to the third electrode 14, and whose negative electrode is connected to the second electrode 13. Furthermore, this biasing circuit comprises another voltage source, referenced V11, whose positive electrode is connected to the negative electrode of the source V 13 and whose negative electrode is connected to the first electrode 11.
  • the second electrode 13 forms a cathode electrode
  • the third electrode 14 forms an anode electrode
  • the distance X separating the first, 12, and the second 13 electrode is much greater than the distance D separating the second electrode 13 and the third electrode 14.
  • the distance X can be made equal to 3 mm.
  • the small volume of the amplification space 15 makes it possible to choose a distance X, the distance between the first electrode 11 and the second electrode 13, equal to a value very close to the dimension, in this same direction, of the slot Fe in the case of FIG. 1a.
  • the distance X can be made equal to 1 mm in particular in the case in which the gas filling the gas chamber is xenon.
  • the illumination beam is a beam of X-rays, for example having an energy of 50 keV
  • a photoelectron of energy 15 keV and a secondary electron resulting from a radiation of X fluorescence in the gas of energy close to 30 keV, the photoelectron and the secondary electron not being able to be separated in conventional detectors.
  • the appearance of two signals in these detectors results in rejecting the event.
  • the reduction of the distance X to a value of the order of one millimeter has the effect of very greatly reducing the probability of capturing the X fluorescence photon, which therefore makes it possible to eliminate the appearance of a double signal.
  • the ratio ⁇ is made equal to 50.
  • the second electrode is formed by a grid pierced with holes and allows the transmission of the electrons generated in the conversion space 12 towards to the amplification space 15 which, taking account of the field amplitude values and of the amplification distance D, makes it possible to ensure the multiplication of these electrons in the amplification space 15 by an avalanche phenomenon confined to the said amplification length D in order to generate multiplied electrons in the vicinity of the third electrode 14 forming an anode.
  • the third electrode 14 is formed of elementary anodes under conditions which will be described later in the description.
  • a detection circuit 3 is provided, which makes it possible to ensure the detection and counting of the multiplied electrons, this detection and counting circuit 3 being coupled to the elementary anodes forming the anode 14.
  • the configuration of the detector element 1 as shown in FIG. 1a that is to say the values of the said dimensions D and X and the value of the field ratio generated between the amplification space 15 and the conversion space 12, allows a particularly noteworthy functioning in that the electrons created in the gas-filled conversion space 12 are transmitted through the cathode electrode 13 into the amplification space 15 wherein, because of the very high value of the electrical field E 2 , these electrons are subject to an avalanche phenomenon, which is of course confined to the avalanche distance D, which is very small.
  • the avalanche front that is to say the dimension in a direction perpendicular to the direction of the electrical field E 2 , is also very small, at most equal to the multiplication distance D/10 for a gain of 1000.
  • an electron which penetrates into the amplification space 15 is multiplied by successive shocks.
  • the size of the avalanche front is therefore of the order of ⁇ , that is to say D/10.
  • the real dimension of the avalanche patterns generated by the multiplication of each electron in the amplification space 15 reaches at most, in the vicinity of the electrode 14, a value of the order of that of the free path ⁇ of the order to D/10, which makes it possible to achieve a resolution value corresponding to this dimension due to the use of elementary anodes of corresponding size, as will be described hereafter in the description.
  • the collection time of the positive ions can be as long a several tens of ⁇ s as a consequence of which the counting rates are limited to values 100 times lower.
  • the elementary anodes constituting the third electrode forming the anode 14 can be formed by electrically conductive elements, referenced 140 in the said FIG. 1c, these elementary conductors having an axis of longitudinal symmetry referenced YY in this figure.
  • the axis of longitudinal symmetry YY of each electrically conductive element 140 is oriented such that they converge towards the ionizing radiation source S, the point of emission of the illumination beam.
  • the electrically conductive elements 140 are formed by electrically conductive strips formed by copper microstrips having a width which can be between 80 and 200 ⁇ m for example and a thickness of a few ⁇ m. These strips can be made by micro-photogravure and covered with a conductive film of gold or copper. They are formed on an insulating substrate such as an epoxy glass material or a sheet of plastic material such as KAPTON for example.
  • each strip 140 is connected to the detection and counting circuit 3 as will be described in a more detailed manner later on in the description.
  • each elementary electrode 140 is then spaced from an adjacent elementary electrode by an angle ⁇ /N-1 when a number N of electrodes is provided, the elementary electrodes 140 thus being spaced regularly in the angle of divergence of the illumination beam.
  • the electrically conductive elements constituting the elementary anodes 140' may also be constituted by pads distributed along a plurality of longitudinal axes YY, as in the case of FIG. 1c, these electrically conductive element pads each constituting an elementary anode and having a dimension in a direction perpendicular to the direction of the axis of longitudinal symmetry YY substantially equal to the amplification distance.
  • each elementary anode 140' can have a substantially square shape whose side is equal to or less than the multiplication distance D, two successive elementary anodes being spaced, for example, both in the longitudinal direction YY and in a direction perpendicular to this longitudinal direction, by the same distance D.
  • the electrically conductive elements forming the elementary anodes 140' are also spaced regularly in the angle of divergence of the illumination beam.
  • Each elementary anode 140' is of course itself interconnected with the detection and counting circuit 3.
  • the advantage of the said configuration of elementary anodes consists in particular in the fact that, as the avalanche phenomena develop only over the multiplication distance D, it is easy to choose the distribution of these elementary anodes in order to obtain the best precision, whereas in chambers with wires a minimum distance between wires equal to 1 mm is necessary in order to ensure satisfactory functioning.
  • the detection and counting circuit 3 can advantageously comprise a plurality of fast amplifiers 30, each fast amplifier 30 of course being interconnected with an elementary anode 140' and supplying a detection signal for the elementary anode in question.
  • the output of each fast amplifier is, for example, interconnected with a counting and storage circuit 31.
  • the second electrode 13 forming a cathode electrode is advantageously formed by a thin electrically conductive plate.
  • This plate is pierced with holes represented in a non-limitative way by circular holes in FIG. 2b, each hole 130 i being distant from another hole by a pitch P and having a dimension T in order to form an array of holes such as shown in the said figure.
  • the thickness e of the plate is small in comparison with the dimension T of the holes.
  • the electrical field in the multiplication space is then chosen to be sufficient for the electrons to pass through the grid.
  • the pitch P of the array is such that D/10 ⁇ P ⁇ D/3.
  • the biggest dimension T of each hole 130 i is very much greater than the thickness e, in a ratio of greater than 5 and such that: e ⁇ T ⁇ P.
  • the grid constituting the second electrode 13 forming the cathode can be embodied by an electro-formed a grid whose thickness e can be of the order of 2 to 5 ⁇ m, the diameter of the holes being, for example, equal to 20 ⁇ m and the pitch being equal to 25 ⁇ m.
  • electrically insulating spacers referenced 150 in FIG. 1a, must, for large areas, be provided in the amplification space 15 in order to allow the holding of the cathode 13 and of the anode 14.
  • the electrically insulating spacers can be formed by quartz wires, for example, whose diameter corresponds to the multiplication distance D.
  • the high resolution radiographic imaging device which is the subject of the invention, such as described above in the description, makes it possible to carry out high accuracy analyses such as those required for diagnostic applications in mammography.
  • the device which is the subject of the present invention comprises, in the conversion space 12, a multi-channel structure, referenced 121, which allows the capture of the illumination beam and the creation of electrons.
  • the multi-channel structure 121 is provided with a plurality of channels extending in the direction of the first electrical field E1. The ionizing radiation absorbed by the multi-channel structure thus causes the creation of electrons, which ionize the gas which is in the channels and thus release electrons which are accelerated in the corresponding channels and then transmitted through the second cathode electrode 13 into the amplification space 15.
  • a neutral particle such as a gamma ray
  • a neutral particle can have a very low probability of being absorbed in the conversion space 12 in the absence of a multi-channel structure; the presence of such a structure in this conversion space 12 makes it possible to absorb a much higher number of gamma rays by the Compton or photoelectric effect or by the creations of pairs.
  • the electrons ejected from the surfaces of the channels have a path limited by the thickness of these channels. They ionize the gas which is in the tube and release electrons which penetrate into the amplification space 15 as will be described hereafter.
  • the structure 121 is a micro-channels structure provided with parallel channels, referenced 121 i , having at least one opening emerging on a flat surface of this structure.
  • the assembly of these openings forms, on the flat surface of the micro-channels structure, an array of holes at the same pitch P and with the same dimension T as the array of holes 130 i existing on the grid forming the second electrode 13.
  • the flat surface of the micro-channels structure having all of the holes of each channel is placed in the vicinity of the second electrode 13 forming the cathode and, of course, in electrical contact with the latter.
  • an opening of the array of openings of each channel 121 i is placed opposite a hole of the grid 130 i , forming the second electrode 13.
  • the structure 121 shown in FIG. 3b can be formed by glass tubes placed side by side. These glass tubes can have a thickness of the order of 2 ⁇ m and the walls of the latter bear the reference 1211 i .
  • the height h of the assembly that is to say the height of the glass tubes, is of the order of 1 to 2 ⁇ m.
  • a metal deposit of gold can be produced on the faces of the micro-channels structure, this deposit being referenced 1210a in FIG. 3b.
  • the diameter of each channel 121 i taking account of the gold deposit, can be between 10 and 30 ⁇ m.
  • micro-channels structure thus produced makes it possible, for holes of diameter 12 ⁇ m and glass tube walls of 2 ⁇ m for example, to form a structure of which 25% of the volume is occupied by the glass.
  • Such a structure has a average density of 0.7 g/cm 3 whereas, in the absence of a micro-channels structure, the gas present in the chamber, such as xenon for example, at a pressure of 5 bars, has a density of 0.03 g/cm 3 .
  • micro-channels structure 121 thus allows an increase by a factor of 20 in the average density of the material intended to capture the ionizing radiation, and therefore a consequently increased probability of capture.
  • the photoelectrons or Compton electrons generated because of the capture have a high probability of escaping the glass walls and of emerging into the holes or channels 121 i , provided that these photoelectrons have energy higher than a few keV.
  • each hole 121 i can comprise an electrically conductive coating 1212 i having high resistivity.
  • This coating is electrically connected to electrodes constituted by the gold coatings 1210 a and 1210 b each placed on the flat face of the micro-channels structure and a voltage for deflecting electrons in the channels 121 i is applied to the electrodes 1210a and 1210b.
  • Each electron emerging into one of the channels 121 i is then subjected to a deflection phenomenon because of the existence of the electrical field E 3 represented in FIG. 3b.
  • the coatings 1212 i of each channel 121 i can be formed by a film of lead with a thickness of a few tens of Angstroms.
  • the electrical field E3 can be created by an appropriate voltage source V 3 .
  • the ionization electrons released into the channels of the micro-channels structure can furthermore be multiplied, prior to their transfer into the amplification space 15, by using the conversion space as one of the multi-stage chambers such as proposed by Selling Georges CHARPAK.
  • the said micro-channels structure can be used either with lateral inlet of the illumination beam, as shown in FIGS. 3a and 3b, or with frontal inlet of the illumination beam, as shown in FIG. 3b, in order to detect soft X rays, in particular for the purpose of carrying out crystallographic analysis tasks.
  • the elementary anodes can be constituted by first parallel conductive strips 140 i , 140 k , to 140 N , taken to the same electrical potential V REF , as described in above in the description.
  • a circuit for coupling by electrical influence is formed by second conductive strips 141, 142, 143 and the following ones, these second strips being perpendicular to the first ones, regularly spaced, and giving rise, by an electrical influence phenomenon of charges in motion, to a signal whose sign is opposite to that appearing on the first strips 140 k .
  • the electrons collected on the conductive strip 140 k for example radiate over one or more strips 141, 142, 143 . . . , those located close to the impact of the electrons on the strip 140 k , the strip 142 for example, a variable electrostatic field which suddenly disappears when these electrons are collected by the conductive strip 140 k , which allows the production on the strips 140 k and 142 of a position pulse of positive sign and a two-dimensional reference X, Y, of the point of impact.
  • the first and second conductive strips can be formed on a substrate made of insulating material and of appropriate thickness, the dimensioning of the thickness, width and spacing of the strips being determined experimentally.
  • the second anode electrode 14 can be formed on a board of electrically insulating material, of the printed circuit type, on the upper face of which, opposite the amplification space 15, are placed the elementary electrodes 140 k described above in the description.
  • the detection and counting circuit 3 may furthermore comprise an electrostatic detection circuit, placed in the extension of the strips 140 k forming elementary anodes, a variant embodiment of the one shown in FIG. 4a, each reference 1410, 1420, 1430 corresponding for example to an electrically conductive strip.
  • This electrically conductive strip is subdivided according to a periodic pattern into two elementary strips whose electrostatic coupling with each elementary anode 140 k are an increasing and decreasing function respectively of the row k of the elementary anode to which each elementary strip 1410, 1420, 1430 is coupled.
  • the elementary strip 1410 for example is subdivided into two elementary strips 1410 a 1410 b whose electrostatic coupling with each elementary anode 140 k are an increasing and a decreasing function respectively of the row of the strip in question.
  • a circuit such as shown in FIG. 4d, makes it possible to measure the amplitude of the end signal, generated at the end of the first 1410 a and of the second 1410 b elementary strip, and the ratio of the end signals. This ratio is representative of the row of the elementary anode, row k, in the vicinity of which the ionization electrons have induced the corresponding electrical pulse.
  • a second strip 1420 can be provided, this strip also being an electrically conductive strip and subdivided into a first 1420 a , and a second, 1420 b , elementary strip according to a same periodical pattern whose periods are multiples of the first electrically conductive strip 1410 in a given ratio.
  • a third strip 1430 can be provided, which is itself subdivided into elementary strips 1430 a , 1430 b .
  • the spatial period of the third strip 1430 is also a multiple of the first electrically conductive strip in another ratio.
  • the circuit shown in FIG. 4d makes it possible to measure the amplitude of the signals generated by the capacitive coupling at the end of the first 1410 and of the second 1420 elementary strip and the amplitude ratio of these end signals.
  • the first and second electrically conductive strips 1410, 1420, associated if applicable with the third electrically conductive strip 1430 which is itself subdivided into two elementary strips 1430 a , 1430 b thus form a measuring system of the vernier type, of the row k of each elementary anode 140 k located substantially opposite the firstly emitted ionization electrons.
  • the circuit 3 for detecting and counting is considered to comprise a logic circuit of the controlled switch type, the circuits 3140 representing amplifier circuits, the circuits 3141 representing analog to-digital converters and the circuit 3142 representing a conversion table making it possible to supply the row k of each elementary anode 140k on which the pulse was detected.
  • a set of electrodes 1410, 1430 forming a capacitive detection circuit, for a one-dimensional detection of the elementary anodes 140 k can be provided in order to produce, in the same way, a capacitive detection circuit for a one-dimensional detection of the second elementary strips, 140, 141, 142 . . . and the following ones, in the second direction.
  • This set of electrodes is then placed on an extension of the elementary strips 140, 141, 142 and the following ones, as in the case of the elementary anodes 140 k .
  • the gas contained in the gas chamber can be xenon mixed with a "quenching" agent such as CO 2 or ethane at a pressure between 10 2 and to 10 6 Pa or, if necessary, a mixture of argon and methane in a volumetric ratio of 90% argon and 10% methane.
  • a quenching agent such as CO 2 or ethane at a pressure between 10 2 and to 10 6 Pa or, if necessary, a mixture of argon and methane in a volumetric ratio of 90% argon and 10% methane.
  • the gas contained in the gas chamber 10 can be constituted by a mixture of argon and triethylamine, in order to make it possible to cause, in the amplification space 15, a multiplication of the electrons by the luminous avalanches phenomenon.
  • the elementary anodes are formed by transparent electrically conductive elements allowing the transmission of the light generated by the luminous avalanches thus created.
  • the detection and counting circuits 3 are for example constituted by a brilliance amplifier 330 b , equipped with appropriate optics 300 a , followed by an integrator system 310, such as a photosensitive film or a CCD camera system for example.
  • the CCD camera brilliance amplifier assembly 300 a , 300 b , 310 is then placed on the surface of the electrode making it possible to transmit or change the wavelength of luminous avalanches phenomenon thus generated, 280 nm in the case of triethylamine in the visible light range.
  • the elementary anodes can be formed by an electrically conductive grid associated with a surface allowing either the transmission of the light at the wavelength of the luminous avalanche phenomenon, or the changing of the wavelength of the luminous avalanche phenomenon into a wavelength in the visible range spectrum.
  • the electrically conductive grid such as shown in FIG. 5b can be formed by conductive wires, gold-plated tungsten wires of diameter 15 ⁇ m with a rectangular pitch of 50 ⁇ m ⁇ 50 ⁇ m.
  • Each elementary transparent 50 ⁇ m zone in fact constitutes the equivalent of an elementary anode through which the luminous energy of the luminous avalanche created is transmitted.
  • This grid can also be constituted by a grid similar to the second electrode 13 shown FIG. 2b.
  • the said grid can then be placed against a UV/visible light converter.
  • the grid as shown in FIG. 5b is of course taken to the reference potential V REF and thus constitutes the anode constituted by an assembly of transparent elementary anodes.
  • the gas chamber is then closed by the intermediary of a quartz window or of a window made of plastic material for example.
  • This improvement appears to be very important when the detection is not made strike by strike by means of electronic circuits, but by means of an integration of luminous photons.
  • Such an operating method is especially important when the emission source S delivers a very intense burst of X or ⁇ rays, an emission source such as a linear accelerator used in radiotherapy. In such a case, it can be necessary to display simultaneously hundreds of thousands or millions of avalanches, which cannot be achieved with conventional electronic means. It is then possible to use, as a particles/ionizing electrons converter, a micro-channels structure, such as described above in the description, or a lead-bismuth matrix such as described in the article published by A. P. JEAVONS, G. CHARPAK and R. J.
  • luminous detection constitutes a means of obtaining high accuracy, in particular when appropriate optics 300 a , a brilliance amplifier 300 b and a CCD camera for example, 310, are used.
  • the illumination beam can be inlet either laterally, in accordance with the method shown in FIG. 1a, or frontally, as shown in FIG. 1b.
  • a measurement can be taken every 50 ms, that is one frame duration of the CCD camera used, whilst one displacement of the detection module is carried out.
  • a frontal inlet appears particularly appropriate when the detection module comprises, in the conversion space 12, a micro-channels converter and the image is acquired of all of the avalanches generated by a pulse or “flash" of ⁇ rays, such as used in radiotherapy by means of a linear accelerator emitting ⁇ rays for very short periods.
  • a pulse or “flash” of ⁇ rays such as used in radiotherapy by means of a linear accelerator emitting ⁇ rays for very short periods.
  • a good image resolution is obtained directly without any need to carry out image processing such as calculation of the centroid, the optical centre of gravity, of each avalanche, as previously proposed by Whatever Georges CHARPAK.
  • This operating method therefore makes it possible to obtain a great saving in equipment and calculating time in comparison with the devices of the prior art.
  • the device which is the subject of the present invention can be used to great advantage in ⁇ radiography, in specific conditions which will be described hereafter, with reference to FIG. 5c.
  • the ionizing radiation source consists in this case of an electrophoresis gel, a section or a preparation, bearing the reference G, the gel, the section or the preparation being radioactively marked in the conventional way.
  • the electrophoresis gel G is then the site of points of emission of ⁇ rays distributed over the cross-section of the gel, the section or the preparation, the illumination beam then consisting of a plurality of ⁇ beams emitted sporadically at these various emission points.
  • the gel G is placed in the vicinity of the window Fe for a frontal inlet of the illumination beam.
  • a support SUP represented by dotted and dashed line in FIG. 5c makes it possible, if necessary, to position the gel, the section or the preparation for observation.
  • the detector which is the subject of the present invention, that latter is such that the first electrode 11 and the second electrode 13 are distant by a distance X close to or less than that of the distance D separating the second electrode 13 from the third electrode 14.
  • the conversion space 12 and the amplification space 15 thus have a substantially equal dimension in the direction perpendicular to the electrodes 11, 13 and 14.
  • the total thickness of the detector 1 is then 0.2 mm.
  • a ⁇ ray emitted from any emission point in the gel G has, as shown in FIG. 5c, a maximum path of the order of magnitude of the distance X separating the first and the second electrodes 11,13.
  • the accuracy of location of the corresponding emission point is better than the value of this distance X.
  • the detector device which is the subject of the present invention makes it possible to develop devices which are simpler than the present devices having chambers with parallel faces in which the location of the point of emission of the ⁇ ray is carried out by means of the variable gain according to the depth of the ionization electron along the z coordinate.
  • FIGS. 6a and 6b A more detailed description of a high resolution radiographic imaging device using X or ⁇ ionizing radiation making it possible to carry out analyses of three-dimensional images in a single exposure will now be given with reference to FIGS. 6a and 6b.
  • the radiation source used S is considered to generate an ionizing radiation beam in the form of a divergent beam having a given solid angle ⁇ .
  • the radiographic imaging device comprises a collimator CO comprising a plurality of longitudinal slots, referenced F 1 . . . F i , . . . F n , forming a plurality of diaphragms in fact making it possible to deliver a plurality of flat illumination beams as shown in the said figure.
  • Each flat illumination beam is distributed substantially in a plane containing one of the longitudinal slots of the assembly of these slots and the source S.
  • the planes containing one of the flat illumination beams together form a beam of planes converging towards the ionizing radiation source.
  • the device according to the invention comprises a module for detecting the set of flat illumination beams, which have made it possible to illuminate the subject to be observed SU, this subject being placed downstream of the collimator CO.
  • This detection module comprises a detector of ionizing particles such as previously described in the description with reference to FIGS. 1a to 5b, this detector 1 being placed facing a corresponding flat illumination beam.
  • each detector referenced 1 1 , 1 i to 1 n , corresponds to a slot F 1 , F i to F n , and in particular, the window Fe 1 , Fe 1 to Fe n of each of these detectors, being the window for the inlet of the flat illumination beam, is placed in the plane formed by the ionizing radiation source S and the slot Fi delivering that flat illumination beam with which this detector is associated.
  • the windows Fe i can be formed, as shown in FIG. 6b in a common collimator CO'.
  • FIGS. 6a and 6b it can be observed that the assembly of detectors 1 1 to 1 n is inclined symmetrically with respect to a central detector referenced 1 i in the said figures.
  • these detectors can be provided with protections, referenced 1 1i , these protections being constituted by a sheet of lead or tungsten making it possible to ensure the independence of each of the detectors 1 i with respect to the ionizing radiations diffused by each adjacent flat illumination beam.
  • the detector 1 used has a very small thickness.
  • the total thickness is of the order of 1.1 mm.
  • this specific characteristic of the high resolution radiographic imaging device which is the subject of the present invention makes it possible to use a device comprising multiple detectors such as shown in FIGS. 6a and 6b. These detectors operate as if they were in parallel and the multiplication of detectors, when a number n of detectors is used, makes it possible to save scanning time of the subject SU, in a corresponding ratio n.
  • n detectors can be placed in a single pressurized gas chamber with lead separating screens, the screens 1 1i being those mentioned above in the description, the latter preventing any secondary radiation produced in a detector from disturbing detection in the adjacent detectors.
  • the detectors 1 used can comprise, instead and in place of the micro-channels structure 12, mentioned above in the description, a plurality of thin inclined sheets, such as tantalum sheets placed at a grazing angle of incidence, of the order to 1°, with respect to the average direction of the illumination flux of ionizing particles, according to a known technique of the prior art. These sheets make it possible to ensure the conversion of the particles.
  • This embodiment makes it possible, on the one hand, to increase the probability of capture of the ionizing particles and of ejection of the photo-electrons thus generated, in accordance with the technique of the said prior art but, on the other hand, thanks to the use of the very high counting rate capability of the detectors 1 according to the subject of the present invention, to reduce considerably the operating costs of the particle accelerator generating the ionizing particles used.

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US6373065B1 (en) * 1999-04-14 2002-04-16 Digiray Ab Radiation detector and an apparatus for use in planar beam radiography
US6389103B2 (en) * 1999-12-29 2002-05-14 Xcounter Ab Method and an apparatus for radiography and a radiation detector
US6414317B1 (en) * 1999-04-14 2002-07-02 Xcounter Ag Radiation detector, an apparatus for use in planar beam radiography and a method for detecting ionizing radiation
US6477223B1 (en) * 2000-03-07 2002-11-05 Xcounter Ab Tomographic apparatus and method
US6518578B1 (en) * 1999-04-14 2003-02-11 Xcounter Ab Method for detecting ionizing radiation, a radiation detector and an apparatus for use in planar beam radiography
US6600161B2 (en) 2000-01-18 2003-07-29 Biospace Instruments Method and apparatus for imaging by means of ionizing radiation
US20030174806A1 (en) * 2002-03-12 2003-09-18 Tom Francke Exposure control in scanning-based detection of ionizing radiation
US20040099810A1 (en) * 2001-07-26 2004-05-27 Jean-Louis Gerstenmayer Ionising radiation detector with solid radiation conversion plate, and method for making same
US6878944B1 (en) * 1999-02-24 2005-04-12 Commissariat A L'energie Atomique Two-dimensional detector of ionizing radiation and method for making same
US20050078784A1 (en) * 2003-10-08 2005-04-14 Tom Francke Scanning-based detection of ionizing radiation
WO2009102875A2 (fr) * 2008-02-14 2009-08-20 Varian Semiconductor Equipment Associates, Inc. Appareil pour mesurer des caractéristiques de faisceau et procédé associé
US7639866B2 (en) 2003-06-10 2009-12-29 Biospace Med Method of radiographic imaging for three-dimensional reconstruction, and a computer program and apparatus for implementing the method
EP2186479A1 (fr) 2008-10-24 2010-05-19 Biospace Med Mesure de grandeurs geometriques intrinseques a un systeme anatomique.
US20100177948A1 (en) * 2007-07-04 2010-07-15 Biospace Med Method for Correcting an Acquired Medical Image and Medical Imager
US20100241405A1 (en) * 2007-11-02 2010-09-23 De Guise Jacques A Osteo-Articular Structure
US20110015514A1 (en) * 2008-02-29 2011-01-20 Ecole National Superieure D'arts Et Metiers (Ensam Medical imaging method and system for providing a finite-element model
US20110147603A1 (en) * 2009-12-22 2011-06-23 Yokogawa Electric Corporation Radiation detection apparatus
US20120199752A1 (en) * 2009-10-15 2012-08-09 Eos Imaging Radiographic imaging device and a detector for a radiographic imaging device
WO2014036164A1 (fr) * 2012-08-28 2014-03-06 Kla-Tencor Corporation Tube intensificateur d'image conçu pour corriger l'aberration et réduire l'endommagement par les ions
US9245658B2 (en) 2010-05-06 2016-01-26 Eos Imaging Imaging apparatus and method

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US6365902B1 (en) * 1999-11-19 2002-04-02 Xcounter Ab Radiation detector, an apparatus for use in radiography and a method for detecting ionizing radiation
FR2810769B1 (fr) 2000-06-23 2002-10-11 Biospace Instr Procede et dispositif d'imagerie radiographique pour la reconstitution tridimensionnelle a faible dose d'irradiation
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US6878944B1 (en) * 1999-02-24 2005-04-12 Commissariat A L'energie Atomique Two-dimensional detector of ionizing radiation and method for making same
US20050092928A1 (en) * 1999-02-24 2005-05-05 Commissariat A L'energie Atomique Bidimensional detector of ionizing radiation and manufacturing process for this detector
US6414317B1 (en) * 1999-04-14 2002-07-02 Xcounter Ag Radiation detector, an apparatus for use in planar beam radiography and a method for detecting ionizing radiation
US6518578B1 (en) * 1999-04-14 2003-02-11 Xcounter Ab Method for detecting ionizing radiation, a radiation detector and an apparatus for use in planar beam radiography
US6373065B1 (en) * 1999-04-14 2002-04-16 Digiray Ab Radiation detector and an apparatus for use in planar beam radiography
US6389103B2 (en) * 1999-12-29 2002-05-14 Xcounter Ab Method and an apparatus for radiography and a radiation detector
US6600161B2 (en) 2000-01-18 2003-07-29 Biospace Instruments Method and apparatus for imaging by means of ionizing radiation
US6477223B1 (en) * 2000-03-07 2002-11-05 Xcounter Ab Tomographic apparatus and method
US20040099810A1 (en) * 2001-07-26 2004-05-27 Jean-Louis Gerstenmayer Ionising radiation detector with solid radiation conversion plate, and method for making same
US6873682B2 (en) * 2002-03-12 2005-03-29 Xcounter Ab Exposure control in scanning-based detection of ionizing radiation
US20030174806A1 (en) * 2002-03-12 2003-09-18 Tom Francke Exposure control in scanning-based detection of ionizing radiation
US7639866B2 (en) 2003-06-10 2009-12-29 Biospace Med Method of radiographic imaging for three-dimensional reconstruction, and a computer program and apparatus for implementing the method
US20050078784A1 (en) * 2003-10-08 2005-04-14 Tom Francke Scanning-based detection of ionizing radiation
US20100177948A1 (en) * 2007-07-04 2010-07-15 Biospace Med Method for Correcting an Acquired Medical Image and Medical Imager
US9119555B2 (en) 2007-07-04 2015-09-01 Eos Imaging Method for correcting an acquired medical image and medical imager
US9142020B2 (en) 2007-11-02 2015-09-22 Ecole National Superieure D'Arts Et Metiers (ENSAM) Osteo-articular structure
US20100241405A1 (en) * 2007-11-02 2010-09-23 De Guise Jacques A Osteo-Articular Structure
WO2009102875A3 (fr) * 2008-02-14 2009-11-05 Varian Semiconductor Equipment Associates, Inc. Appareil pour mesurer des caractéristiques de faisceau et procédé associé
US8097866B2 (en) 2008-02-14 2012-01-17 Varian Semiconductor Equipment Associates, Inc. Apparatus for measuring beam characteristics and a method thereof
US20090206273A1 (en) * 2008-02-14 2009-08-20 Varian Semiconductor Equipment Associates, Inc. Apparatus for measuring beam characteristics and a method thereof
WO2009102875A2 (fr) * 2008-02-14 2009-08-20 Varian Semiconductor Equipment Associates, Inc. Appareil pour mesurer des caractéristiques de faisceau et procédé associé
US20110015514A1 (en) * 2008-02-29 2011-01-20 Ecole National Superieure D'arts Et Metiers (Ensam Medical imaging method and system for providing a finite-element model
EP2186479A1 (fr) 2008-10-24 2010-05-19 Biospace Med Mesure de grandeurs geometriques intrinseques a un systeme anatomique.
US20120199752A1 (en) * 2009-10-15 2012-08-09 Eos Imaging Radiographic imaging device and a detector for a radiographic imaging device
US8513616B2 (en) * 2009-10-15 2013-08-20 Eos Imaging Radiographic imaging device and a detector for a radiographic imaging device
US20110147603A1 (en) * 2009-12-22 2011-06-23 Yokogawa Electric Corporation Radiation detection apparatus
US8829459B2 (en) * 2009-12-22 2014-09-09 Yokogawa Electric Corporation Radiation detection apparatus
US9245658B2 (en) 2010-05-06 2016-01-26 Eos Imaging Imaging apparatus and method
WO2014036164A1 (fr) * 2012-08-28 2014-03-06 Kla-Tencor Corporation Tube intensificateur d'image conçu pour corriger l'aberration et réduire l'endommagement par les ions
US9666419B2 (en) 2012-08-28 2017-05-30 Kla-Tencor Corporation Image intensifier tube design for aberration correction and ion damage reduction

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JPH1082863A (ja) 1998-03-31
EP0810631B1 (fr) 2002-09-04
DE69715092D1 (de) 2002-10-10
FR2749402B1 (fr) 1998-08-07
DE69715092T2 (de) 2003-04-30
EP0810631A1 (fr) 1997-12-03

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